The present invention relates to increasing the amount of organic nutrients in ocean water, particularly within a few hundred feet of the surface, so as to increase the production of harvestable food in these near-surface waters. Specifically, this invention concerns itself with a means for artificially inducing an upwelling of relatively nutrient-rich water from the lower depths of the ocean into the relatively nutrient-deficient near-surface waters.
Life on earth depends ultimately on food created by green plant organisms through the process known as photosynthesis. Photosynthesis requires the presence of sunlight, and, in the oceans, sufficient sunlight to support the process of photosynthesis is present only in the water that is less than 100 to 200 meters below the surface. This area where all the ocean's photosynthesis takes place is known as the photic zone. Below the photic zone is the area where there is insufficient light to support photosynthesis, and this zone is known as the aphotic zone.
Because of the presence of sunlight for photosynthesis, the photic zone is the habitat for the minute green plant organisms known as phytoplankton which comprise the first link in the food chain which culminates in those organisms which are consumed as food by man. However, the amount of life which can be sustained in the photic zone is limited by the quantity of such substances as nitrogen, phosphorous, copper, and organic nutrients, which are required to sustain life. In the photic zone these substances are constantly being depleted by the life forms present in the zone and thus the amount of life which the photic zone can support is self-limiting.
However, the above-mentioned life sustaining substances and nutrients are present in constant abundance in the aphotic zone below the photic zone. This is due to the relative scarcity of nutrient-depleting life forms in the aphotic zone. Furthermore, the aphotic zone is constantly enriched in nutrients from decaying organic matter that sinks from the overlying photic zone. Thus, the aphotic zone is, on the average, substantially richer in nutrients than the photic zone.
Therefore, if nutrient-rich water from the aphotic zone can be introduced into the photic zone, the amount of life that could be sustained in the photic zone would be substantially increased. Such a mixing of aphotic zone water and photic zone water is not easily achieved since the aphotic zone water is normally colder and thus denser than the photic zone water and will therefore not normally rise into, and mix with, the photic zone water. However, in a number of areas in the ocean, a variety of natural mechanisms serve to bring the deep aphotic zone water up into the photic zone. These areas are known as "upwelling areas" and they occur in places where offshore winds, equatorial currents, or large ocean waves are strong enough to produce a substantial mixing and churning effect that is sufficient to pull the deep water into the near-surface photic zone. Also, in polar seas, seasonal cooling of the surface water causes the surface water to become cooler and denser than the deeper water and thus an upwelling situation can arise in such areas. Because of the upwelling of nutrient-rich aphotic zone water into the photic zone, these upwelling areas are extraordinarily fertile, and it has been estimated that these upwelling areas support approximately one-half of the total available food fish in the oceans, even though these upwelling areas constitute only a small fraction of the total sea surface.
As the state of the art exists today, there is no practical means for inducing upwelling by means of artificially induced thermal convection currents.